Internal grinding machine



July 13, 1948. A. MATHYS 2,445,146

' INTERNAL GRINDING MACHINE I Filed Jan. 15, 1945 5 Sheets-Sheet 1 July13, 1948. M. A. MATHYS INTERNAL GRINDING MACHINE 5 Sheets-Sheet 2 FiledJan. 15, 1945 jr'zverzfor A/Zaf/J6 y 13, 4 M. A. MATHYs 2,445,146"

INTERNAL GRINDING MACHINE .w q) 7 fiverzor R 4 -MaocA.MaZ/5 s PatentedJuly 13, 1948 INTERNAL GRINDING MACHINE Max A. Mathys, Detroit, Mich.,assignor to Ex- Cell-O Corporation, Detroit, Mich., a corporation ofMichigan Application January 15, 1943, Serial No. 472,444

2 Claims. 1

The present invention relates to improvements in machine tools, and hasparticular reference to automatic internal grinding machines of the typedisclosed in the patents to Blood et al. Nos. 2,011,705 and 2,027,627,issued, respectively, on August 20, 1935, and January 14, 1936.

In internal grinding machines of the aforesaid type, the work spindle isadvanced relatively from a rest position in a rapid approach movementaxially of the grinding wheel into grinding position, then isreciprocated to effect grinding of an internal surface in the workpiece,and, when the workpiece has been ground to the desired depth, isreturned to the rest position. During the grinding operation, a relativeprogressive cross-feed is imparted to thegrinding' wheel. Axialseparation of the workpiece and the grinding wheel may be efiected at anintermediate point in the grinding operation to permit wheel dressing.

Entry of the grinding wheel into the workpiece at the start of the cycleand also after dressing, and withdrawal thereof from the workpiece fordressing and again at the end of the grinding operation, presents aproblem when the workpiece has an internal lip or other obstructionwhich the grinding wheel must pass to reaclf the range of grindingreciprocation. The primary object of the present invention is to providean automatic internal grinding machine in which the grinding wheel isautomatically retracted transaxially from the normal line. ofreciprocation for each entry of the wheel into the work, and eachwithdrawal thereof from the work so as to avoid interference with anyobstruction on the workpiece in its normal path of movement.

A more specific object is to provide a new and improved grinding machineof the foregoing character in which the reciprocatory movements, thecross-feed movements, and the retract movements between the workpieceand the grinding wheel are synchronized throughout the machineoperation.

Other objects and advantages will become apparent as the descriptionproceeds.

In the accompanying drawings,

Figure 1 is a front elevational view of a grinding machine embodying thefeatures of my invention.

Fig. 2 is a plan view showing the relationship of the work and toolspindles.

Fig. 3 is a diagrammatic representation of the hydraulic transmissionsystem incorporated in the machine.

Fig. 4 is a diagrammatic representation of the electrical drive andcontrol system incorporated in the machine.

The internal grinding machine, disclosed for purposes of illustration,comprises a main base l on which a table 2 is mounted for reciprocationfrom a rest position at the left into a grinding position at the right.The table may support or the work to be either the grinding wheelground. In the present instance, a work spindle 3 is mounted on thetablel, and has. a suitable chuck 4 for supporting a workpiece A. Thechuck 4 is adapted to be released by a mechanism (not' fully shown)having an operatin handle 5 for the purpose of loading the roughworkpiece and removing the finished workpiece.

Different kinds of workpieces having internal ribs or projectionslocated outwardly of the surface to be ground may be machined. In thepresent instance, the workpiece A is shown as the outside race of a ballbearing consisting of a cylindrical sleeve 6 having a conical raceway 'Iat the inner end. Due tothe conical or tapered form of the raceway 1,the spindle 3 is adjusted at an angle to the line of reciprocation asshown' in Fig. 2, and as a result the outer end of the sleeve 6 islocated in the normal path of grinding reciprocation. To gain entry ofthe grinding wheel into position to grind the raceway 1,'it is necessaryfor the wheel to clear the outer end of the sleeve 6.

Mounted on the right end of the base I is a tool head 8 arranged forshifting movement transversely of the table 2. A spindle 9, extendlineof reciprocation of the tool head 8, anding longitudinally of the thetable 2, is journaled in carries a grinding wheel H] on its outer leftend. An electric drive motor II is mounted on the table 2, and isconnected through belts l2 to drive the work spindle 3. shown, may beprovided for driving the grinding spindle 9.

Also mounted on the table therewith and located somewhat in advance ofthe work chuck 4 is a dressing device l3 having a dressing tool Itadapted to be projected into the path of the grinding wheel I0 to dressthe periphery of the latter at a predetermined point in the machinecycle. The dressing device l3 comprises a hydraulic cylinder l5 and apiston l6 reciprocably disposed therein. When the pressure in thecylinder is is relieved through a line H, the piston IB is retracted towithdraw the dressing tool It into an inoperative position.-

When fluid under pressure is supplied through the line ll to thecylinder IS, the piston l6 Any suitable means, not

2 for movement entry of the grinding wheel I0 into the workpiece A inposition to grind the conical raceway 'l, the tool head 8 is shiftedrearwardly to locate the grinding wheel in normal grinding position, andthe work table 2 is reciprocated back and forth in the grinding range ata reduced speed for rough grinding. At the end of the roughing cut, thegrinding wheel I0 is again retracted laterally out of engagement withthe workpiece A to avoid interference with the cylindrical sleeve 6, andthe work table 2 is given an amplified or extended movement to the leftto withdraw the wheel from the work past the dressing tool I4. Followingthe dressing operation, the work table 2 is again advanced into grindingposition, and the grinding wheel I0 is returned into cutting engagementwith the work. Thereafter, the work table 2 is reciprocated at a stillfurther reduced speed for finish grinding. A cross-feed is imparted tothe grinding wheel l0 during both rough and finish grinding. When theworkpiece A has been ground to the desired depth, the grinding wheel Ill is again retracted out of the path of the cylindrical sleeve 6, andthe work table 2 is returned to the rest position.

The work table 2 is translated by an automatically controlled hydraulictransmission. In the present instance, the transmission is the same asthat disclosed in the patent to Blood et 9.1., No. 2,011,705, to whichreference may be had for a more detailed understanding of the specificcon-' struction. Briefly described, the hydraulic transmission includesa cylinder 18 mounted in the base of the machine, and a piston l 9reciprocable in the cylinder and having a piston rod 20 connected to thetable 2. Referring to Fig. 3, fluid under pressure is adapted to besupplied by a pump 2| connected through a system of valves to the inletport 22 of a main reversing valve 23. The valve 23 has two outlet portsconnected, respectively, through lines 24 and 25 to opposite ends of thecylinder l8. With the reversing valve 23 in the position shown, fluidunder pressure is admitted to the right-hand end of the cylinder It forurging the table 2 to the left into the rest position, and the fluid inthe left-hand end of the cylinder I8 is discharged through the line 24and the direction valve 23 to an exhaust line 25. It will be understoodthat when the main valve 23 is shifted into the opposite or reverseposition, fluid under pressure will be admitted to the lefthand. end ofthe cylinder ill for urging the table 2 to the right into the grindingposition. and fluid exhausting from the right-hand end of the cylinderwill pass through the line 25 and valve 23 to the line 26.

The line 24 is connected to the left end of the cylinder [3 through achannel 21 adapted to be blocked when the piston I9 nears the left-handposition, and also through an inlet check valve 28 opening to theextreme end of the cylinder. As aresult, fluid under pressure is free topass to the left end of the cylinder [8 at all times upon appropriateadjustment of the valve 23,

4 but upon movement of the piston l9 into its lefthand position, thechannel 2'! will be blocked to cushion the movement of the table 2 as itis brought to rest.

The hydraulic transmission system includes a series of valve structuresfor automatically controlling the rate at which fluid under pressure issupplied from the pump 2| tothe hydraulic actuator during differentportions of the machine cycle. The inlet port 22 of the main valve 23 isconnected through a line 29 to a manually adjustable orifice valve 30having a relatively large orifice 3| for receiving fluid during therapid approach, and a relatively restricted orifice 32 for controllingthe rate of reciprocation during rough grinding. The selection of theorifices 3i and 32 is under the control of a rate control valve 33having an adjustable spool plunger 36. Upon adjustment of the plunger 34into the right-hand position shown in Fig. 3, the pressure line 35 ofthe pump 2| is connected directly to a line 36 opening to the relativelyunrestricted orifice 8!. Upon movement of the plunger 34 one step to theleft, the inlet to the line 36 is blocked so that the relativelyunrestricted orifice 3! is rendered inoperative.

The valve 33 is also connected through a line 3'! to a dresser controlvalve 38 having an adjustable spool plunger 39. When the plunger 39 isin the left-hand position of adjustment as shown in Fig. 3, the valve 38connects the line 31' from the valve 33 to a line 40 connected with therelatively restricted orifice 32 in the orifice valve 30, and alsoconnects the cylinder I5 of the wheel dressing device l3 to exhaust. Theconnection from the cylinder [5 is through the line H, the valve 33, aline 4| and the valve 38 to a drain line 42. In the right-hand positionof adjustment of the plunger 39, the valve 38 serves to block the directconnection between the lines 31 and 40, and to establish a connectionthrough an adjustable orifice 43, the orifice serving to control therate of movement of the work table 2 during the dressing operation. Inthis position, the valve 38 also serves to connect the line 4| to thepressure inlet line 3! so that fluid under pressure is supplied to thecylinder 15 to render the dressing device 13 operative.

It will be understood that the valves 23, 33 and 38 are operatedautomatically in timed sequence in the course of the machine cycle.' Thevalve 23 has a hand lever 44 for starting the cycle, and isautomatically oscillated through dogs (not shown) on the table 2 toreciprocate the table when in grinding position.

In the initial approach movement of the table 2, the valve plunger 34occupies the right-hand position and the valve plunger 39 occupies theleft-hand position as shown in Fig. 3 so that fluid under pressure fromthe pump 2| is directed through the lines 35 and 36, the large orifice3| and the line 29 to the main control valve 23, and then through theline 24 to the left end of the cylinder l8 so as to efiect movement ofthe table 2 to the right at a rapid rate. As the table reaches thegrinding position, the valve plunger 34 is shifted one step to the leftinto an intermediate position, thereby blocking the connection to the Iline 36, and the valve plunger 39 is unchanged.

' stop and rapid the {rough grinding operation, the valve plunger 36 isadjusted into its right-hand position to project the dresser plunger [1,and the leftward movement of the table 2 is extended to effectseparation of the workpiece A from the grinding wheel In in a dressingstroke at a rate determined by the setting of the dressing controlorifice 43. Upon reentry of the grinding wheel l6 into the workpiece A,the valve plunger 34 is adjusted into its left-hand position, and theplunger 39 is returned into its left-hand position. As a result, fluidis directed from the pump 2| through the line 35, the valve 33, the line31, the valve 38, the line 46 and the orifice 32 in the valve 36 to thepipe 29, but the plunger 34 serves to restrict the fiow area between thelines 35 and 31 so that the rate of travel of the table 2 is reduced forfinish grinding.

Movement of the work table 2 to the left beyond the grinding rangedetermined by the reversing dogs for the main valve 23, first, in thedressing stroke and, later, in the return stroke to rest position, iseffected by a shiftable control bar (not shown) operable by ahydraulicactuator 45 under the control of two solenoid valves 46 and 41. Theactuator 45 comprises a cylinder 48 having fluid supply lines 49 and 50opening to opposite ends. A piston is neciprocable in the cylinder 48,and is formed in one end with a recess 52. A second piston 53 alsoreciprocable in the cylinder 48 and adapted to enter the recess 52, andhas a rod 54 extending from one end of the cylinder for operating theaforesaid control bar.

The solenoid valves 46 and 41 are of the spring centered type, and areshiftable respectively against the action of the spring means bysolenoids SVI and SV2. Each of the valves has a connection with thepressure line 35 of the pump 2|, and with exhaust lines 55. The valve 46also has a connection with the line 56 to the large end of the cylinder48 and the valve 41 has a connection with the line cylinder 48.

When both solenoids SVI and SV2 are energized, as shown in Fig. 3, fluidunder pressure from the line 35 is directed through the valves 46 and"to both lines 49 and 50 to opposite ends of the cylinder 48 so that therod 54 is fully projected. This is the condition which prevails duringthe approach movement of the work table 2. When both are deenergized asthey are during rough and finish grinding, the valves 46 and 41 connectopposite ends of the cylinder 48 through the lines 49 and 50 to theexhaust lines 55 so that the rod 54 is in its innermost retractedposition. When only the solenoid SVI is energized, the valve 46 servesto connect the cylinder line 50 to the pressure line 35, and the valve41 serves to connect the cylinder -line 49 to the exhaust line 55 sothat the piston 53 is actuated to project the rod 54 one step outwardlyto institute extended movement of the work table 2 in the dressingstroke. At the end of the grinding operation, both solenoids SV 1 andSV2 are again energized to fully project the rod 54 so as to institutethe return movement of the work table 2 into the rest position.

A cross feed movement is imparted to the tool head 8 during the grindingreciprocation of the table 2 un=til the workpiece A is ground to finaldepth. This cross-feed is imparted automatically to the tool head 8 bya. cross-feed mechanism fully disclosed in the aforesaid patent toBloodat al. No. 2,027,627 to which reference may be had for 49 to the rod,end of the 'a more detailed understanding. Briefly described, the crossfeed mechanism is operable through a. gear rack 56 by a hydraulicactuator 51 a. cylinder 58 and. a p'ston 59. The rod end of the cylinder58 is'open to a line 60 adapted for connection by the valve 33 to thepressure line 35" during the stop and rapid approach movements of thework table 2', and to an exhaust llne 6|- during .the grindingoperation. The other end of the cylinder 58 is open to a line 62 adaptedto be connected to an exhaust line 63 by a valve 64 when the line so isconnected to pressure, and to be blocked from said exhaust line by saidvalve when the line 60 is connected to exhaust.

The line 60 is also connected by a selection valve 65 to receive fluidthrough either or both of two adjustable restricted orifices 66 and 61from a line 68 leading from the valve 38. During rough grinding, thevalve 65 is positioned to connect both orifices 66. and 61 between thelines 62 and 66 so that a relatively large volume of fluid is suppliedto the actuator 51 to impart a comparatively rapid cross-feed to thegrinding wheel l0. During fin-'- lsh grinding, the valve 65 is adjustedto cut out the orifice 66 so as to reduce the rate of cross-feed. Duringdressing, the flow is throttled by the ori-' fice 43. Resetting of thecross-feed mechanism may be accomplished by a hand valve 69 forconnecting the line 62 to the line 68.

Lateral retraction of the-grinding wheel [6 to avoid interference withthe workpiece A upon each axial entry, reentry and withdrawal, isobtained by shifting the tool head 8 without disturbing the cross-feedadjustment. The means for this purpose includes a lever (not shown)operable by a hydraulic actuator 10 having a cylinder 1| and a piston 12therein. The piston 12 has av rod 13' extending from one end of thecylinder 1| for connection to the retract mechanism. The large end ofthe cylinder 1! is open to the line 56 for connection to pressure by thevalve 46 when the solenoidSVl is energized to effect wheel retraction,and for connection to exhaust when the solenoid is deenergized for roughand finish grinding. The other end of the cylinder 11 is connected to anexhaust line 14. A switch LS1 for controlling the work spindle motor IIis operable by a hydraulic actuator 15 connected across the lines 35 and66. Hence, the switch is closed during the grinding and dressingoperations, and is open during the rapid approach movement of the worktable.

Electrical control circuits and operation Electric current for anelectric motor 16 for driving the hydraulic pump 2|, a coolant pumpmotor 11, and the work spindle motor H, is sup-,- plied from main linesL1, L2 and L3 upon closing a main switch 18., The lines L1 and L3areconnectedthrough a transformer 19 to control circuits havingsupplylines L4 and L5.

The hydraulic pump motor 16 and the coolant pump motor 11 are adapted tobe connected to the lines L1, L2 and L3 by normally open con, tacts H1adapted to be'engaged upon excitation of relay coil H by closing amanual starting switch 80. When the starting switch is closed, thecircuit for the coil H is completed from the line L4 through th coil H,the starting switch '80, a normally closed manual stop switch BI, andtwo normally closed parallel limit switches LS5 and LS6 to the line L5.The limit switch LS5 is arranged to open only when the grinding wheel 10is worn down. The limit switch LS6 is opened when the work table 2 isall the way out in its rest,

position. .Energization of the coil H serves to close holding contactsH2 across the starting switch 80.

Adapted for connection across the lines L4 and Ls are a pluralityofrelay coils W, CRI CR3, CR2 and TR'I. The circuit, for the relay coil Wis adapted to be established upon closing of the limit switch LS1, thecircuit being from the line L4 through the coil W, the limit switch-LS7,the holding contacts Hz, the stop switch 81, and the limit switches LS5and LS6. It will beevident that ii the relay coil H is not excited, thecircuit for the relay coil W cannot be completed. Upon excitation of therelay coil W, contacts Wiare closed to connect the work spindle motor Hto the lines L1, L2 and L3. Also adapted to be connected across thelines L4 and L5 are thetwo solenoids SW and SVZ for actuating the valves46 and 41 respectively.

The relay coil CR! controls three normally open contacts C-Rll, CRl2and.CRl-3. The relay coil CR3 controls normally closed contacts CBS-.1and CR3-3, and normally open contacts ORB-2., CR3--l and CHE-r5. Therelay coil CR2 controls normally closed contacts CR2-| and normally opencontacts CR22. The relay coil TRl isadapted upon energization to close atimingswitch 'IRl-Al When the table is at the rest position, the relaycoil CR3 will be energized, the circuit having been completed in theprevious cycle upon closing the timing relay switch TRI-I and the limitswitch L'Sl, which is closed when the table 2 is all the way forward.The relay CR3 consequently has closed contacts CR3-2 to maintain thecircuit through the contacts LS3--A of the limit switch LS3. ContactsCR3-I are open to disable the circuit for the relay coil CRI,andcontacts CR3-3 are open to disable the holding circuit for the relaycoil CR2. Contacts CR3-4 and CRii-li are closed so that the solenoidsSVI and SV2 are energized.

To initiate the machine cycle, the starting valve 23 is shifted manuallyinto the starting position, and thereupon the table '2 starts on itsrapid traverse forward movement to the right. Since during the approachboth solenoids SV! and SV2 are energized, the grinding wheel in islocated in laterally retracted position to permit entry into theworkpiece A without interference with the forward end of the cylindricalsleeveis. At the end of the approach movement of the table 2, with thegrinding wheel Ill located within the workpiece A in position to grindthe conical raceway l, the limit switch LS3 is actuated momentarily toopen the contacts LS3A and to close the contacts LSZi-B, therebybreaking the circuit for the relay coil CR3, and as a result opening thecontacts CHE- l and CR3-5 to break the circuits for the solenoids SVIandSV2. Upon deenergization of the solenoids, the grinding wheel I0 isshifted laterally into cutting engagement with the workpiece A. At thesame time, the valve plunger 34 is shifted into its rough grindingposition, thereby connecting the large end of the cylinder to drain toclose the limit switch LS'l, and the rod end of the cylinderii't todrain to institute the cross-feed. Closing the limit switch LS7completes the cir cuit for the'relay coi-l W to close contacts W1 in the:circuit for the work spindle motor H.

The table 2 is now reciprocated in the grinding range at a reduced speeddetermined by the orifice 32, and the grinding spindle 9 is given across-feed to grind the raceway l in a roughing operation. At the end ofroughgrinding, the

limit switch LS2 is closed, and then at the end of the forwardreciprocation of the table 2, the limit switch LS1 also is closed,thereby establishing a circuit for the relay coil CRI, from the line L;through the coil CRI, the contact CR2,-I and CR34 and the limit switchesLS2 and LSI to the line L5. Excitation of the relay coil CRI closescontact CRI-l vto establish a holding circuit across the limit switchesLSl and LS2; also closes contacts CRl-2 in the circuit for the relaycoil CR2 to prepare the circuit for subsequent completion; and closescontacts CRl-3 to establish the circuit for the solenoid SVI.Consequently, the grinding spindle 9 is retracted to separate thegrinding wheel ill from the conical raceway lor the workpiece A, and thepiston 5| is actuated to project the, rod 54 partially outwardly so asto cause the table 2 to move through an extended dressing stroke. At thesame time, the valve 38 is shifted to direct fluid to the cylinder l5 sothat the dressing tool M will take a cut across the periphery of thewheel It). After reentry of the wheel in into the workpiece A in thereturn dressing stroke, the limit switch LS3 is actuated momentarily toclose the contacts LS3B, thereby establishing a circuit for the relaycoil CR 2, Energization of the relay coil CR2 serves to close contactCR2-2 to establish a holding circuit across the contacts ORA-2 andLS3-B, the contacts CR33 at this time beingin closed position, The relaycoil CR2 also opens contacts CR2-l to interrupt the circuit for therelay coil CRl, and upon deenergization of the latter, the contactsCRl-l, CRl-2 and URI-3 are opened to deenergize the solenoid SV! andagain move the grinding wheel Ill laterally into engagement withtheworkpiece A.

' Thereafter, the grinding cycle continues in a finish operation untilthe desired size is reached, at which time the limit switch LS4 isclosed by the cross-feed of the tool head 8 to complete the circuit forthe timing relay TRI. After a predetermined delay, during whichthecross-feed is stopped by a positive abutment, the rela coil T-R'lcloses the contacts TRII. As soon as the table 2 then reaches the end ofits forward travel in the final grinding stroke, the limit switch LSI isclosed, thereby again completing a circuit for the relay coil CR3.Energization of the relay coil CR3 serves to open the contacts CR3I andCR33 to interrupt the circuits for the relay coils CR! and CR2, andserve to close holdin contacts CR3-2, and contacts CR3-4 and CR'35,again energizing the solenoids SVI and SV2. As a result, the grindingwheel I'll .is retracted from the finished surface of the workpiece A,and the piston 53 is actuated to fully project the rod 54 so as toinstitute return movement of the'table 2 into rest position remote fromthe grinding wheel.

' I claim as my invention:

v1; A grinding machine comprising, in combination, a base, atraverseslide mounted for reciprocation on said base, a cross-feed slide mountedon said base for transverse movement, a rotary work spindle mounted onone of said slides for supporting a workpiece having an internal surfaceto be ground, a rotary spindle supporting a grinding wheel and mountedon said other slide, means for automatically advancing said traverseslide in an approach movement from a position external of said workpieceto an operative grinding position, and then reciprocating said traverseslide with said grinding wheel in engagement with said surface, andmeans including a hy-- draulic actuator controlled by anelectricallyoperated valve for maintaining said grinding wheel laterallyretracted out of line with said surface during said approach movement,and electric control means for said valve including a limit switchactuated by said traverse slide to efiect movement of said grindingwheel laterally into cutting engagement with said surface after'entry ofsaid wheel into said workpiece.

2. A grinding machine comprising, in combination, a base, a traverseslide mounted for reciprocation on said base, a cross-feed slide mountedon said base for transverse movement, a rotary work spindle mounted onone of said slides for supporting a workpiece having an internal surfaceto be ground, an electric motor for driving said spindle, a rotaryspindle for supporting a grinding wheel and mounted on said other slide,means for automatically advancing said traverse slide in an approachmovement from a remote position to an operative position, and thenreciprocating said traverse slide in a grinding range, means including ahydraulic actuator for maintaining said grinding wheel laterallyretracted out 10 of line with said surface during said approach movementand for shifting said grinding wheel into normal position after entryinto said workpiece, and electric control means including a limit switchoperable hydraulically to complete the drive circuits for said motorupon entry of said wheel into said workpiece.

MAX A MATHYS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,816,082 Heald et a1. July 28,1931 1,826,178 Kempton et a1 Oct. 6, 1931 1,997,978 Raule Apr. 16, 19352,011,705 Blood et a] Aug. 20, 1935 2,027,627 Blood et al Jan, 14, 19362,029,511 Steiner et a1. Feb. 4, 1936 2,127,856 Blood Aug. 23, 19382,156,970 Burns May 2, 1939

